When the HEMT device adopts the group III nitride semiconductor, the two-dimensional electron gas with a high concentration can be formed in the heterostructure, such as AlGaN/GaN, due to the piezoelectric polarization and spontaneous polarization effect. In addition, the HEMT device can obtain very high electric field strength for dielectric breakdown, and a good characteristic of high temperature resistance by adopting the group III nitride semiconductor. The group III nitride semiconductor HEMT device with a heterostructure can be used as a high frequency device, and is applicable for high-voltage/high-current power switching devices.
When the existing group III nitride semiconductor HEMT device is used as a high frequency device, or a high-voltage and high-power switching device, the output current of the drain electrode is often unable to keep up with the changes of the gate control signal, a large turn-on transient delay is caused, that is a “current collapse phenomenon” on the group III nitride semiconductor HEMT device, which seriously impacts the practicality of the device. The existing comparatively acknowledged perception on the “current collapse phenomenon” is “virtual gate model”. In the “Virtual gate model”, when the device is in a turn-off state, an electron is injected into the surface of the semiconductor, so as to form as a virtual gate with a negative charge through surface state or defect capture. The virtual gate with a negative charge will reduce the channel electron in the gate-drain and gate-source access region due to electrostatic induction. When the device is transformed from a turn-off state into a turn-on state, although the channel under the gate can quickly accumulate a large number of electrons, the charge in the virtual gate cannot be timely released. The concentration of channel electron under the gate is low, so the output current at the drain end is small. Only when the charge in the virtual gate is fully released, the current at the drain end can be restored to a level of the DC state. At present, the ordinary used methods for suppressing “current collapse” comprise: reducing the density of surface state or interface state by performing the surface treatment on the semiconductor, reducing the electric field strength of the gate electrode adjacent to one end of the drain electrode through a field plate structure, reducing the probability of electron captured by defects, and suppressing the current collapse. However, the effect of the method of suppressing the current collapse under a high current and a high voltage is not ideal.